No but for most people it would be 3-4 units. It also makes a huge difference if you have eaten or not. A lot of factors and not worth taking any risks if you are unsure.
1 unit per hour. You would have to be over 3-4 units to test over the limit. A 14% bottle of Red 10 units, go to bed at 12 drive at 8 am , 2 units left = ok. It all depends on alcohol tolerance, effectiveness of liver, body size etc, all in all if you have had a session, say 6 pints of premium...